Production of polyesters using basic ferric acetate as catalyst



'with "splitting out of glycol. ""has'not been entirely satisfactory becausethe initial ester -interchange reaction is slow and because many of the PRODUCTION OF POLYESTERS USING BASIC FERRIC ACETATE AS. (ZATALYST John Sullivan, Akron, hio,-'-assiguor to The Goodyear Tire & Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. ApplicationJun 17,1954,

Serial No. 437559 I 12. Glaims. (Cl.260"-75) This inventionrelates tothe:preparation ofpolymeric glycol esters of .terephthalic and .isophthalic acids. More particularly this invention relates to. an ,improvement in In the preparation of linear superpolyesters, .one of the plicity of reaction and economy of operation has been theester. interchange method in which the esters of the acids are reacted with a glycol to form the diglycol ester 1 of the'acid or a low molecular weight polymeric polyester which is. then polymerized to a 'high molecular weight polymeric polyester by 'a'c'ondensation reaction This process, however,

materials that catalyze this reaction are not effective as catalysts for the subsequent-condensation reaction.

Heretofore various materialshavebeen proposed as catalysts for the ester interchange reaction between the esters of dicarboxylic acids andglycols an'dfo'rthe subsequent polymerization or condensation reaction. Metals in the form of powder, chips, ribbon or wire have been suggested, as have surface catalysts such as broken glass or silica gel. The more successful of the catalysts used in the past, however, have been the alkaline materials such as the alkali metal and alkaline earth metal alcoholates, the alkali metal carbonates, or other alkaline reacting salts, alkaline earth oxides, and litharge.

Many of these materials are effective catalysts for the initial simple ester interchange, and some of them catalyze the condensation reaction. However, many of the substances that catalyze the condensation reaction carry the polymerization only to a low degree or they do not promote the reaction effectively enough to give reaction rates acceptable for a commercial process.

According to the present invention, it has been found that basic ferric acetate (Fe(0H)2(C2H3O2)) catalyzes the ester interchange between glycols and terephthalate esters or isophthalate esters or mixtures of these esters and greatly accelerates the subsequent polymerization of the product and permits the formation in relatively short reaction times of polymers of high molecular weight which may be readily processed to form products having excellent properties.

Therefore, the terephthalate or isophthalate ester or a. mixture thereof can be reacted with a glycol and the resultant glycol ester condensed to form a polymer, both stages of the reaction being carried out in the presence of basic ferric acetate. However, the his glycol ester may be prepared by any other suitable method, such as by reacting the sodium or potassium salt of the acid with ethylene chlorohydrin, or by reacting the acid with a large excess of the glycol, or by glycolysis using some catalyst which is a catalyst for the ester interchange but which is not a catalyst for the polymerization reaction.

2,740,768 PatenteiApr, 3, l 1956 The following example illustratest the invention and how ittmay be carried out:

Example Twelve parts of ethylene glycol and 12 parts of a 75/25 dimethyl terephthalat'e/dimethyl isophthalate mixture to which 0.0038 part of basic :ferricacetate had beenadded were placed in a glass tube having an inside diameter of millimeters. The mixture of polyesterforming reactants was heated to 197 C. under nitrogen gas at atmospheric pressure. A slow stream of. nitrogen was passed through the mixture at the rate ofapproximately 100 bubbles per' minute." Stirring was accornplished by mechanically rotating themitrogen' inlet tube .most satisfactory. methods from the standpoint of simwhich was fitted with three-pairs of blades". The alcoholysis was carried substantially -to completion asdetermined by the recovery ofapproximately 90% of the cal- -.culated amount of methanol. The timerequired for the alcoholysis reactionwas 3.5 hours. At-theconclusion of the alcoholysis the pressure was gradually reduced to 0.1 millimeter of mercury and the unreactedglycol distilled" off. By-controlling the rate of flow of nitrogen into the evacuated system, the pressure was. controlled and maintained at 1.0 millimeter of mercury. After 5.5

hours of condensation at 260 and 1 millimeter of mercury a /25 ethylene terephthalate/ethylene isophthalate copolymer having a melt .viscosity at 280 C. of 19,620 poises was obtained.

' other ratio of ethylene terephthalate't'o ethylene isophthalate can'similarly be made u'sin'g basicferric acetate as catalyst for the ester interchange or polymerization re action, by adjusting the proportions of the starting mateials.

In the practice of the invention, the preparation of the glycol ester and its subsequent polymerization is, in general, carried out in accordance with the usual, known techniques. Thus, the reaction is preferably carried out in the absence of oxygen, generally in an atmosphere of an inert gas such as nitrogen or the like, in order to lessen darkening and to make it possible to obtain a high molecular weight pale or colorless product. Bubbling the inert gas through the reacting mixture serves the added functions of agitation and of expediting the removal of volatile components formed by the reaction.

The amouunt of basic ferric acetate used my be varied over wide concentrations. As is usual with catalysts, the amount will ordinarily be relatively small. As a general rule, the amount will be within the range of from 0.003 to 0.10 percent, based on the dialkyl phthalate or other phthalate diester. The preferred range is 0.003 to 0.05 percent, based on the dialkyl phthalate or other phthalate diester used, to give a satisfactory reaction rate and a product of suitable viscosity and color.

The example given illustrates the invention particularly with respect to the dimethyl esters and ethylene glycol. The invention will also work effectively with other esters of the phthalic acids such as the ethyl, propyl, butyl, and phenyl esters. Other glycols, such as the propylene glycols and the butylene glycols may also be used although ethylene glycol is preferred because of its low cost and ready availability.

While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

I claim:

1. In a process for preparing a polyester by the selfcondensation, with the removal of a glycol, of a his glycol ester of at least one acid selected from the group consisting of terephthalic acid and isophthalic acid, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of basic ferric acetate.

2. A process according to claim 1 in which the basic ferric acetate is used in amount of 0.003 to 0.05% by weight of the weight of the esters of terephthalic acid and isophthalic acid.

3. In a process for preparing a polyester by subjecting at least one bis ester of an acid selected from the group consisting of terephthalic and isophthalic acids to alcoholysis in the presence of an excess of a glycol and thereafter subjecting the bis glycol ester thus formed to self-condensation, with the removal of glycol, the improvement which comprises carrying out both the alcoholysis and condensation in the presence of a catalytic amount of basic ferric acetate.

4. A process according to claim 3 in which the basic ferric acetate is used in amount of 0.003 to 0.05% by weight of the weight of the esters of terephthalic acid and isophthalic acid.

5. In a process for preparing a polyester by the selfcondensation, with the removal of ethylene glycol, of a his ethylene glycol ester of at least one acid selected from the group consisting of terephthalic acid and isophthalic acid, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of basic ferric acetate.

6. A process according to claim 5 in which the basic ferric acetate is used in amount of 0.003 to 0.05% by weight of the weight of the esters of terephthalic acid and isophthalic acid.

7. In a process for preparing a polyester by subjecting at least one his ester of an acid selected from the group consisting of terephthalic and isophthalic acids to alcoholysis in the presence of an excess of ethylene glycol and thereafter subjecting the bis ethylene glycol ester thus formed to self-condensation, with the removal of ethylene glycol, the improvement which comprises carrying out both the alcoholysis and condensation in the presence of a catalytic amount of basic ferric acetate.

8. A process according to claim 7 in which the basic ferric acetate is used in amount of 0.003 to 0.05% by weight of the weight of the esters of: terephthalic acid and isophthalic acid.

9. In a process for preparing a polyester by the selfcondensation, with the removal of ethylene glycol, of a his ethylene glycol ester of terephthalic acid, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of basic ferric acetate.

10. In a process for preparing a polyester by the selfcondensation, with the removal of ethylene glycol, of a bis ethylene glycol ester of isophthalic acid, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of basic ferric acetate.

11. In a process for preparing a copolyester by the self condensation, with the removal of ethylene glycol, of a mixture of bis ethylene glycol terephthalate and bis ethylene glycol isophthalate, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of basic ferric acetate.

12. In a process for preparing a high molecular weight polyester by the self-condensation, with the removal of ethylene glycol, of a low molecular weight ethylene glycol polyester of at least one acid selected from the group consisting of terephthalic and isophthalic acid, the improvement which comprises carrying out said condensation in the presence of a catalytic amount of basic ferric acetate.

References Cited in the file of this patent UNITED STATES PATENTS 2,465,319 Whinfield et a1 Mar. 22, 1949 

1. IN A PROCESS FOR PREPARING A POLYESTER BY THE SELFCONDENSATION, WITH THE REMOVAL OF A GLYCOL, OF A BIS GLYCOL ESTER OF AT LEAST ONE ACID SELECTED FROM THE GROUP CONSISTING OF TEREPHTHALIC ACID AND ISOPHTHALIC ACID, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID CONDENSATION IN THE PRESENCE OF A CATALYTIC AMOUNT OF BASIC FERRIC ACETATE. 